(a) Field of the Invention
The present invention relates to a method and apparatus for activating and deactivating a serving cell.
(b) Description of the Related Art
A carrier aggregation technology is a technology for expanding service bandwidth, and a terminal may simultaneously receive services through a primary cell and a plurality of secondary serving cells.
Recently, according to a dual connectivity technology which is being discussed in the 3GPP standardization, the terminal may simultaneously receive services through serving cells of different base stations in which a backhaul delay occurs.
According to the carrier aggregation technology according to the related art, the primary serving cell of the terminal maintains an activation state and the secondary serving cells of the terminal are controlled in an activation state or a deactivation state by an activation/deactivation medium access control (MAC) control element (CE) or secondary serving cell deactivation timers (sCellDeactivationTimer) which are set in each of the secondary serving cells. The secondary serving cells which are added to the terminal maintain the deactivation state by an RRC signaling message. When the terminal receives the activation/deactivation MAC CE which represents the activation of the secondary serving cells set in the terminal, the corresponding secondary serving cell is activated, and when the terminal receives the activation/deactivation MAC CE which represents the deactivation of the secondary serving cells set in the terminal, the secondary serving cell is deactivated. The activation/deactivation MAC CE instructs the activation or the deactivation of the serving cell set in the terminal.
FIG. 1 is a diagram illustrating the activation/deactivation MAC CE according to the related art, in which the terminal performs an activation procedure on the secondary serving cell set as a secondary serving cell index i when a Ci value of the activation/deactivation MAC CE is set to be 1, and performs a deactivation procedure on the secondary serving cell set as the secondary serving cell index i when the Ci value is set to be 0. The Ci is an individual field which instructs the activation or the deactivation of the secondary serving cell set as the secondary serving cell index i which is allocated to a specific terminal.
When the secondary serving cell set in the terminal is activated, the terminal transmits a sounding reference signal (SRS) to the corresponding secondary serving cell, reports channel state information (CSI) on the corresponding secondary serving cell, and performs monitoring of a physical downing control channel (PDDCH) of the corresponding secondary serving cell.
When the secondary serving cells set in the terminal are deactivated, the terminal stops SRC transmission to the corresponding secondary serving cell, stops the CSI report to the corresponding secondary serving cell, and stops monitoring of the PDCCH of the corresponding secondary serving cell.
When the terminal receives uplink allocation information or downlink allocation information through the PDCCH of the secondary serving cell, the terminal restarts the secondary serving cell deactivation timer. When the terminal receives the uplink allocation information or downlink allocation information on the secondary serving cells through the PDCCH of the serving cell which schedules the secondary serving cells, the terminal restarts the secondary serving cell deactivation timer.
The carrier aggregation technology according to the related art may secure synchronization of deactivation timer values of the secondary serving cells and the activation and deactivation states of each of the secondary serving cells between the primary serving cell and each of the secondary serving cells, under an inter-cell aggregation environment in which a backhaul delay does not occur.
However, there is a problem in that the deactivation timer values of the secondary serving cells and the activation and deactivation states of each of the secondary serving cells which restart depending on whether each of the secondary serving cells is scheduled in a TTI unit under the cell aggregation environment between the base stations in which the backhaul delay occurs are not determined in the serving cells of the different base stations in real time.
Further, the activation/deactivation MAC CE includes not only activation and deactivation indicators of the serving cell of the base station transmitting the activation/deactivation MAC CE but also activation and deactivation indicators of serving cells of other base stations. Therefore, when the activation/deactivation MAC CE is transmitted from each of the base stations to the terminal in the state in which the activation and deactivation states of the serving cells between the base stations mismatch each other, the terminal performs the activation or deactivation procedure of each of the serving cells set in the terminal depending on the activation/deactivation MAC CE, such that the states of the serving cells between the base stations and the terminal mismatch each other.
Further, under the cell aggregation environment between a master Enb (MeNB) which manages connection information of the terminal and manages traffic transmitted to the terminal and a slave Enb (SeNB) additionally set for traffic transmission to the terminal, in the case in which data are transferred from the MeNB to the SeNB, when the MeNB does not transfer the data to the SeNB in the state in which the serving cell of the SeNB set in the terminal is in an activation state, the serving cell resource of the SeNB is unused and thus a load of the MeNB may not be dispersed, and if the MeNB continuously transfers the data to the SeNB in the state in which the serving cell of the SeNB set in the terminals is in the deactivation state, a buffer of the serving cell of the SeNB may overflow.
Therefore, a method for efficiently activating and deactivating a serving cell in the inter-cell aggregation environment in which the backhaul delay occurs and a method for sharing activation and deactivation state information on the serving cell between the base stations in which the backhaul delay occurs are required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.